Security readout for executives and security teams
Plain-English summary
Older Nextcloud Server versions could leave a deleted user’s WebAuthn login token behind. If the same username was later reused, the former user might be able to access the new account. This is a high-impact identity lifecycle flaw, but the source bundle does not show active exploitation.
Executive priority
Treat this as a priority patch for affected Nextcloud environments, especially those with staff turnover, shared naming conventions, or automated account provisioning. The issue can cross account boundaries, but the required conditions make emergency response dependent on local exposure.
Technical view
CVE-2021-32726 affects Nextcloud Server before 19.0.13, 20.0.11, and 21.0.3. WebAuthn tokens were not removed when users were deleted, allowing token carryover if usernames were recreated. CVSS 3.1 is 7.1 with high confidentiality, integrity, and availability impact, high attack complexity, low privileges, and required user interaction.
Likely exposure
Exposure is likely where affected Nextcloud versions were used with WebAuthn enabled and operational processes allowed deleted usernames to be reused. The risk is narrower than broad remote compromise because it depends on a prior user, retained token, and username reuse.
Exploitation context
The bundle lists no CISA KEV entry and no cited source proving active exploitation. Practical abuse requires a previous user whose WebAuthn token remained registered, deletion of that user, and later reuse of the same username by another person.
Researcher notes
The core security failure is stale authentication material surviving account deletion. Evidence is strong for affected versions and fixed releases, but public exploitation evidence is not present in the supplied bundle. Do not broaden impact beyond username reuse with retained WebAuthn tokens.
Mitigation direction
- Upgrade Nextcloud Server to 19.0.13, 20.0.11, 21.0.3, or later.
- Follow Nextcloud advisory guidance; sources state there are no known workarounds.
- Avoid reusing deleted usernames until the affected instance is upgraded.
- Review recently deleted and recreated accounts for WebAuthn registration risk.
- Prioritize systems where WebAuthn and external user lifecycle automation are used.
Validation and detection
- Inventory Nextcloud Server versions across production and managed environments.
- Confirm affected instances are upgraded to a fixed or later release.
- Review whether deleted usernames were later recreated during the affected period.
- Check recreated accounts for unexpected WebAuthn registrations or unusual access.
- Validate user deletion behavior in staging after applying the fixed release.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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Open ATT&CK lookupCVE-2021-32726 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H1.25.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.1HighVector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-6qr9-c846-j8mgCVE reference · x_refsource_CONFIRM
- https://github.com/nextcloud/server/pull/27532CVE reference · x_refsource_MISC
- https://hackerone.com/reports/1202590CVE reference · x_refsource_MISC
- GLSA-202208-17CVE reference · vendor-advisory, x_refsource_GENTOO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Incorrect Ownership Assignment
Incorrect Ownership Assignment represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.